Localizer beacon



A.n G.. KANDOIAN LOCALIZER BEACON Filed Sept. 27, 1940 4 Sheets-Sheet lATTORNEY.

May 19, 1942- A. G. KANDolAN l V2,283,677

LOCALIZER BEACON Filed Sept. 27, 1940 4 Sheets-Sheet 2 CURRENT\4RELAnvE/-Qw PHASE 2 l RELATIVE INVEN TOR. `ARM/Cv', G. /fA/VDOMN BY TTORNEY.

May i9, 1942.

A. G. KANDOIAN LocALizER BEACON Filed Sept. '27,` 1940 4 Sheets-Sheet 32 RELATIVE -J CURRENT 4 RELAT/VE 4:90" PHASE POWER FROPORTlO/V//VGSOURCE 0F CARR/ERF NODULATED WITH J EowEn PEoPanr/oN/Ne /vErwonn INVENTOR.

/PM/G 6. MNM/AN ORNEY.

19, 1942. K A. G. KANDolAN 2,283,677

LOCALIZER BEACON Filed Sept. 27, 1940 4 Sheets-Sheet 4 Patented May 19,1942 i UNYE.

STATES Frtiibi'i' GFFHCE LOCALIZER BEACON Application September 27,1940, Serial No. 358,677

(Cl. Z50- 11) 6 Claims.

My invention relates to radio beacons and more particularly to twocourse beacons of controllable sharpness for defining a course line orlanding direction.

Systems of antennae are known wherein a central radiator provided withother radiators on either side thereof are used to define a course. Inthese systems the central radiator provides an on course signal and theside radiators provide the identifying patterns on either side of thecourse, this latter pattern being termed the clover leaf pattern sinceit is generally of a four lobe shape. In this known system the sharpnesswhich can be obtained is limited by the permissible spacing of the sideradiators as these must be so chosen that the signal does not reduce tozero at any point except on course, as otherwise other points of equalsignal intensity of cross-overs will occur giving rise to false courses.i

In accordance with my invention I provide a system of two course beaconsgenerally of the same type as that described above, and in addicoursepatterns.

Fig. 7 shows an arrangement for supplying energy to the systems inaccordance with my invention, and

Fig. 8 shows a modified arrangement wherein the pattern adjusting effectis produced by ar single radiator or array.

in Fig. 1 is shown a beacon array comprising a central radiator C andtwo equally spaced side radiators A and B. This represents a previouslysuggested system` wherein the central radiator is energized preferablywith signal modified carrier energy the signals being either modulationor keying signals which are used to dene the These signals may be, forexample 9G cycle and 150 cycle frequencies or interlocking Morse codesignals such as A--N. The side radiators are then energized, vforexample, so that for the 90 cycle side band currents A and B are appliedat 90 and +90 phase, respection provide other side radiators to increasethe sharpness of the course signals. This may be accomplished by varyingthe number of radiators, changing the relative energization of thevarious side radiators with respect to one another or by varying theenergization of the central radiator with respect to the side or cloverleaf radiators.

It is accordingly a principal object of my invention to provide a beaconwherein the desired degree of sharpness may be obtained.

It is a further object of my invention to provide a two course orlocalizer beacon having a high degree of sharpness and a reducedradiation in undesired directions.

It is a still further object of my invention to provide a beacon systemusing an auxiliary radiator or radiators for controlling the sharpnessof the beacon.

Other objects and advantages of my invention will be apparent from aparticulardescription thereof made in connection with the accompanyingdrawings in which Fig. l is a diagram for explaining the operation of aradio beacon of known type.

Fig. 2 is a diagram of a beacon array used to explain the generalprinciple of my invention.

Figs. 3 and 4 are patterns produced by the side radiator-s alone and thecombination of side radiators and the central radiator, respectively,using two extra side radiators in accordance with my invention.

Fig. 5 shows a modied beacon pattern produced by a system using widerspacing of the added side radiators.

Fig. 6 shows a further modied system using additional side radiators.

tively, with respect to C and for the 150 cycle side band current A andB are energized at +90 and 90 phase, respectively, with respect to C.While above it is implied that side band energy only is .fed toradiators A and B, carrier energy may also be applied to theseradiators. This arrangement produces a beacon having a staticdistribution which may be expressed:

F(0)=1+2/l cos (S10 sin 0)=*= 2Ka sin (S10 sin 0) where Fw) is afunction varying with angular displacement 0 about the center ofsymmetry, generally termed the primary radiation function of antennaarray, S10 is the spacing in electrical degrees from the outer radiatorto the center radiator, Ka is the current intensity in antennae A and Bassuming unity current in C, and ,c is the ratio of induced current inside radiators to primary current in center radiators, 0 is thehorizontal angle from the normal to the axis of the radiator.

` For simplicity of discussion the radiation pattern from the centralradiator may be considered as circular which means ,u equals 0, so thatthe rst term of Equation 1 reduces to unity. Then Equation l reduces tothe simplified form:

F(0)=1i2Ka sin (S10 sin 9) (2) With this form of beacon there will betwo courses without any cross-overs, that is points Y duced by radiatorsl, 2, 3, 4

f2(0)=[K1 sin (S1 sin 0)-I- K2 (3) sin (Sz sin `{9H-K1. sin (S3 sin9)-i-K4 sin (54 sin 0)-1- Kn sin (Sno sin 0) l2 in the form of a serieswhich may be extended indefinitely, wherein, K1, K2 Kn represent therelative current intensities in the radiators, and S1", S2 Sn representthe spacing in degrees of the respective units from the point ofsymmetry of the system.

For the sake of simplicity a system using just two sets of sideradiators may be taken for purposes of illustration. Then f2(0)=2[K1 sin(S1 sin 0)-l- (4) y K2 sin (S2 sin 0)] Substituting in Equation 2 toobtain the entire beacon pattern The general equation for the total eldpattern may be expressed Where F09) equals the total eld intensity,,13(0) equals the field due to the central radiator, and f2(0) equalsthe lield due to the side or clover leaf radiators.

The requirements for the beacon or localizer based on this generalformula may then be expressed as follows:

1. To prevent cross-overs or false course, due to primary radiations 2.To define sharpness i. e. ratio of right to left signal at a specifiedangle o, in M decibles equivalent to m ratio of intensities 3. To definea minimum ratio of right and left signals for 0d not in the vicinity ofthe course expressed at P decibels or a p ratio of intensities reducingto me a (e 9) for l.5 0s 178.5 for a two course beacon 1.5 6s 88.5' fora four course beacon 4. The minimum signal, on course 6 volts per meternormally f2(0)=0 on course and f1(0)6 for 0:0

By using the values derived in Equations 6 to 'v 10, it is readilypossible to design a beacon having a desired sharpness and withoutcross-overs. Furthermore, if the structure is made symmetrical anexperimental check of the pattern shape may be made readily bymeasurements on the ground at relatively small distances and accordinglywith considerable accuracy.

A further advantage lies in the fact that since the added side radiatorsare generally spaced quite a large distance from the center of thebeacon they may be used to introduce a minimum or virtual null at adesired angle to reduce reflection from external objects.

Reradiation from objects in the field of the beacon may cause errors inthe course indication. This error results from reradiation of energyfrom the side radiators only as can be seen by the following discussion.

Suppose a reflecting object reradiates some signal toward the course andthat this reradiated signal is K/D representing the energy reradiatedfrom an object at D distance and f1(0), fz(0) have the same significanceas given above. On course, the normal signal is 73(0) since f2(0) equalszero. Since the amounts of and 150 cycles in f1(0) are equal, we have anOn course indication. The reradiated K/D f1(0) will obviously change thesignal on course depending upon the phase in which it arrives. However,both the 90 and cycle modulations react exactly the same way, that is,they are either both reduced or both increased. There is, therefore, nochange in course indication.

For iK/D f2(0) this is not the case. Here the plus sign applies to onemodulation (say 90 cycles) While the minus sign applies to the other(say 150 cycles). Therefore, if the 90 cycle signal is increased, whilethe 150 cycle radiation is decreased, the net result is a falseindication in favor of the 90 cycles. At another point along the course,depending upon the source of reradiation, the opposite phaserelationship may prevail, so that the 150 cycle radiation is favored.This, of course, is the cause of the familiar bends and multiplecourses. The magnitude of these undesirable eiects depends upon thestrength of the reradiated signal from the side radiators and not fromthe central radiator. In other words, for a localizer having fixed oncourse signal and fixed sharpness, the amount of trouble to be expecteddue to a given reradiating object is directly proportional to the sideradiator intensity in that direction and nothing else.

The above discussion makes it clear that it is the side radiator groupwhich should receive particular attention in the design of a localizerarray, for it is this signal which must be reduced in the direction of areilecting object when the course is unduly disturbed. The centralradiator radiation does no harm at all. The only reason for reducingthis radiation in directions to the side of the course is to provide agreater ratio between the 90 cycle and 150 cycle signals and to use theenergy more favorably.

One particular example of a beacon station built according to theprinciples of my invention and the field pattern curves thereof isillustrated in Figs. 3 and 4.

In Fig. 3 is shown side or clover leaf radiators only. The two radiatorsI, I' are each spaced a distance of from the center of symmetry and theouter center radiators 2, 2' are each spaced 720 from the center. Usingthe same symbols, namely, K1, K2 to denote the relative current valuesin radiators I, I' and 2, 2, the ratio is chosen equal to .4. With thisform of radiator a curve such Aas shown in solid line curve 3i isproduced. The dash line 3i) illustrates the clover leaf radiationpattern obtained with only two radiators such as I, I'. Only the fieldpattern on one side of the beacon is shown, it being understood that thepattern on the other side is symmetrically disposed. It can be seen thatby the use of the two additional radiators the curve has been greatlysharpened along the zero line. In Fig. 4 the complete field pattern ofthe beacon adding together the clover leaf pattern of Fig. 3 and acircular central radiation pattern from the central radiator I is shown.This pattern is produced using the same specifications for the outer orclover leaf radiators as used in Fig. 3 and energizing the centralradiator H) with current intensity of 1.52 compared to one for the sideradiators I, I. The course is defined by the two radiation patterns d0,4I which overlap at the center zone. It can be readily seen that thisarrangement provides a very sharp course beacon, the sharpness of whichmay be specified as about 4.3 decibels for a l.5 departure from the`course.-

To obtain higher degree of sharpness the ratio of nay be made larger-This may be accomplished by increasing the current in radiators 2, 2'and since they then will add a larger value to the original curve 3i!they will clearly provide a sharper course. Increased sharpness may alsobe obtained by decreasing the current in the central radiator. rIhelimit of this sharpness, however, is reached when the central radiatorobtains a value approaching zero. This latter method is not alwaysdesirable since it results in considerably less signal on the course. Itshould be borne in mind that the ratio should be maintained at a valuegreater than unity so that the clover leaf pattern will not drop to zeroat any point except along the course line. Otherwise, false courses maybe defined by the system.

The course may also be sharpened by increasing the spacing S2, that is,increasing the spacing of the outer radiators 2, 2', with respect to thecenter of symmetry. A curve showing the effect of such increased spacingis shown in Fig. 5.

The pattern of Fig. 5 is produced by an array comprising a centralradiator I0, and side radiators I, 2 and l', 2', the current ratio inthe central radiator and side radiators is proportioned 1.52, 1, .4respectively, as indicated. The radiators I, I' are spaced 160electrically from the central radiator and the outer radiators 2' arespaced 1440 electrically from the central radiator. With thisarrangement a sharpness of '7.7 db. per 1.5 departure from course isobtained. It can beseen, therefore, that a considerable improvement insharpness is obtained by this increase in spacing. However,

the patterns have the characteristics that a relatively great amount ofpower is radiated at angles to the course line. This generallyrepresents wasted power and furthermore may cause undesirable effectsdue to reflection from objects located at an angle to the course line.In many cases, however, this added radiation is not objectionable.

The sharpness of the course may also be increased by adding other sideor clover leaf radiators as shown in Fig. 6. In this arrangement thecentral'radiator I0 is provided with three auxiliary or side radiatorsI, 2, 3, I', 2', 3', arranged on eith'er side thereof. The pattern likethe others discussed is produced using a circular central radiationpattern. The current relation may be expressed, I0, 2.12; I, I', l; 2,2', 1, and 3, 3', .5, and the spacing in electrical degrees from thecentral radiator is, I, I', 210; 2, 2', 480, and 3, 3', 780. y

The beacon sharpness produced by this arrangement is 8.58 db. per 1.5departure from course. Furthermore this arrangement has the advantageover the arrangement shown in Fig, 5 in that additional lobes are notproduced thereby and the pattern may be made much more smooththroughout. Furthermore, by properly adjusting the spacing of theseadditional radiators the pattern may be so adjusted as to have asubstantial minimum or null in a particular direction so as to avoidharmful reflections from outside objects.

It is clear that the antenna arrangements disclosed in Figs. 3 to 6,inclusive, may be made up of single radiators of any form, for example,vertical dipoles or antennae designed for producing horizontallypolarized waves as disclosed in the` application of Andrew Alford, Ser.No. 2'70, 173, filed April 26, 1939. However, it is also clear that eachof the radiators may be made directional if desired, it being merelynecessary in this case to substitute the desired values for thedirection parameters of the system in the various equations whencalculating the curves. Moreover, the central radiator may be composedof more than one unit, it being merely necessary that this radiator bemaintained symmetrical with respect to the clover leaf pattern.

A symmetric arrangement showing a preferred constructional arrangementfor a five-element beacon, such as shown in Fig. 4, is illustrated inFig. 7. In this figure the central radiator I0 and the side radiators I,I', 2, 2' are shown as antennae for producing horizontally polarizedwaves. Two sources of carrier modulated with frequencies F1, F2,respectively, are shown at 90, Si. It is clear that these two sourcesmay comprise modulators fed from a common transmitter of high frequency.These sources 9D, 9| are connected over a bridge network 92 so as tosupply the carrier and both modulating side bands to the centralradiator I0 in phase. From the opposite side of the network leads 33convey the side band energization containing modulators F1 and F2 to theantennae I, I', 2, 2' The energy from source F1 is supplied so as to bein phase opposition in units I, 2, and I', 2' and the line is adjustableso that these currents are ahead and 90 behind the correspondingcomponent in unit I0. The carrier F2 is supplied to the same radiatorsbut with phase reversed with respect to the energy of F1. Powerproportioning networks 94, are provided so as to properly proportion theenergy in radiators I, 2, I', 2 with respect to the energy in radiatorI0. With this system a complete control of the beacon arrangement so asto obtain the desired ratio of currents may be readily achieved.

From these particular examples illustrated, it is clear that by usingthe principles of my invention the degree of sharpness of a beacon maybe controlled at will by selecting thedesired number of elements andarranging their spacing and energization. By adding still furtherelements to the system shown in Fig. 6, for example, even greatersharpness may be obtained. In general in the system shown theenergization ratio K1 etc., should not exceed unity between any twoelements of the array.V However, particularly when a large number ofelements are used this particular condition need not be satisfied foral1 the elements.

In the system described above, each of the arrangements shown haveconsisted of a symmetrical arrangement of antennae elements. Asharpening of the course may be obtained if desired by providing onlyone set of antenna elements spaced on one side of the main beaconradiator, these elements being energized so as to carry both themodulation frequencies. Such an arrangement is disclosed in Fig. 8. Inthis figure a network similar to that shown in Fig. 7 supplied fromsources 90, 9|, is shown, furnishing the energy for a central radiator Iand two side radiators I. In place of the additional side radiators 2,2', however, a single unit |00 is provided composing in this case twoantenna elements |0I, |02; Energy is supplied to these units fromsources90, 9|, in such phase relation that the signals from F1 will add tothose components on the left side of the beacon course and subtract fromthe right side thereof and the energy from F2 will add .to thosecomponents on the right side of the course and subtract from the leftside thereof. Thus, a symmetrical pattern is produced having the desiredincrease in sharpness similar to that shown in the arrangement of Figs.3 and 4.

For this unsymmetrical system the total radiation T(0) at any angle 0 isgiven by the equation T09) =F2(0) -I-G2(0) i2G(0) F(0) sin (do Sin 0) inwhich Fw) is the primary radiation function, that is, the radiation fromthe principle antenna, G09) is the auxiliary radiation function, that isfrom the auxiliary radiator system, and d0 is the spacing between themain and the auxiliary radiators.

This system has the advantage of economy in structure over the priorsystems, since it requires only one additional radiating unit"l insteadof units on each side of the array. This system produces a greatincrease in sharpness of the course indiction but has the disadvantagethat the eld pattern cannot be readily determined by ground measurementsexcept at large distances from the beacon since there is no symmetricalarrangement of units. .Furthermore with this arrangement the clover leafradiating pattern no longer has a zero component along the course line,but has a slight component along the line. An arrangement such as shownin Fig. 8 has been constructed and proven quite satisfactory inoperation.

In this system the spacing between the central radiator I0 and the sideradiators I, was substantially 165 and the spacing between the center ofthe radiator and the auxiliary radiator |00 was made substantially 24'at 109 megacycles corresponding to about 2.8 wavelengths. Energy wassupplied for radiator |00 from the supply leads feeding the other sideradiators. With this arrangement a sharpness of substantially 5 decibelsper degree and .one-half departure from course wasobtained. This is asubstantial improvement compared with previous arrangements wherein asharpness of 2.28 decibels per degree one-half has been obtained.

While, in the arrangements described in connection with Fig. 8, theauxiliary radiator |00 has been dened as being energized at 90 withrespect to the central radiator, it is clear thatl this is not anecessary limitation, it being merely necessary that the phase relationof F1, F2 leading and lagging, the currents in central radiator I0,respectively must be equal if symmetrical patterns are to be obtained.Accordingly, the present structure lends itself most readily to anarrangement wherein the 90 relationship is maintained. However, byutilization of suitable phase Shifters, other relationships, forexample, say leading and 85 lagging may be obtained. In this case theenergy is most easily supplied directly from lines interconnecting thesources 9|)V and Si with network 92.

It is evident that the arrangement as disclosed above provides a systemwhereby a beacon may be calculated to provide the desired sharpness ofcourse as well as reduction of radiation in particular directions.

While I have disclosed by way of example only a few preferredembodiments thereof, it should be distinctly understood that this is notto be considered as a limitation on the scope of my invention. What Iconsider my invention and desire to protect in this application is setforth in the accompanying claims.

What I claim is:

1. A radio beacon comprising an array of antennae, a source of radiofrequency energyf means for modulating said source with signal energy oftwo distinctive signal characteristics, means for applying saidmodulated energy to said array to effect a radiation of said energy toproduce a course indication by comparison of said distinctive signals,and means for modifying the sharpness of said course indicationcomprising an auxiliary radiator spaced from said array of antennae, andmeans for applying energy modulated with both said signals to saidauxiliary radiator with an energy level differing from that supplied tothe antennae of said array.

2. A radio beacon comprising a central radiating means, radiating meansspaced on either side of said central radiating means, two sources ofradio frequency energy characterized by distinctive signals, means forapplying energy from said sources to said central radiator in aparticular phase relation, means for applying signal energy from one ofsaid sources substantially in phase quadrature with respect to saidcentral radiating means and in phase opposition to said other radiatingmeans, means for applying signal energyfrom the other of said sources tosaid other radiating means in opposite phase to the energy applied fromsaid one of said sources, whereby a beacon course of predeterminedsharpness is defined, and means for increasing the sharpness of saidcourse comprising additional radiating means spaced from said centralradiating means and each of said other radiating means, and means forapplying signal energy to said additional radiating means from both saidsources with the same phase relation as said spaced radiating means, andwith an energy level lower than that applied to said other radiatingmeans.

3. A radio beacon comprising a central radiating means and a pluralityof auxiliary radiating means disposed on each side thereof, and meansfor energizing said central radiating means in a predetermined phaserelation and said auxiliary radiating means on one side in phaseopposition with respect to those on the other side and in phasequadrature with respect to said central radiating means, said auxiliaryradiating means being energized With different current intensities fromthe current intensity of the central radiating means and with differentrelative current intensities from one another.

e. A radio beacon comprising a central radiating means, a plurality ofauxiliary radiating means spaced on each side of said central radiatingmeans, means for energizing said central radiating means with energy,means for energizing said auxiliary radiating means on opposite sides ofsaid central radiating means in phase opposition with respect to eachother and in phase quadrature with respect to said central radiatingmeans, the field pattern being dened by the equation 17(0) =1(0)i|K1 sin(S1 sin 0) -I-Kz sin (S2 sin 0) +Kn sin (Sn sin 0)] where is the`angular relation of the radiation, F09) the resultant total pattern,f1(0) the pattern from the central radiating means, K1, K2 K" therelative current intensities of the energy in n, auxiliary radiatingmeans on each side of center of symmetry of the system, and S1, S2" Sn"the relative spacing in electrical degrees from the center of symmetryof said respective auxiliary radiators, the energy at the centralradiating means being greater than zero.

5. A radio beacon comprising a central radiating means and a pair ofauxiliary radiating means disposed on each side thereof and in linetherewith, said auxiliary radiators nearest said central radiator beingspaced therefrom a distance in the order of one-half a Wavelength, meansfor energizing said central radiating means in a predetermined phaserelation and said auxiliary radiating means on one side in phaseopposition With respect to those on the other side and in phasequadrature With respect to said central radiating means, and means forenergizing said auxiliary radiating means nearest said central'radiating means with different current intensities from the currentintensity of the central radiating means and said other auxiliaryantennae with current intensities different from said nearest auxiliaryradiators.

6. A radio beacon comprising a central radiating meansy radiating meansspaced on either side of said central radiating means a distance in theorder of one-half a wavelength, two sources of radio frequency energycharacterized by distinctive signals, means for applying energy fromsaid sources to said central radiator in a particular phase relation,means for applying signal energy from one of said sources substantiallyin phase quadrature with respect to said central radiating means and inphase opposition to said other radiating means, means for applyingsignal energy from the other of said sources to said other radiatingmeans in opposite phase to the energy applied from said one of saidsources, whereby a beacon course of predetermined sharpness is defined,and means for increasing the sharpness of said course comprisingadditional radiating means spaced from said central radiating means andeach of said other radiating means a distance of at least one wavelengthfrom the central radiator, and means for applying signal energy to saidadditional radiating means from both said sources with the same phaserelation as said spaced radiating means, and with an energy level lowerthan that applied to said other radiating means.

ARMIG G. KANDOIAN.

